Concurrent removal of Cu(II), Co(II) and Ni(II) from wastewater by nanostructured layered sodium vanadosilicate: Competitive adsorption kinetics and mechanisms

Wastewater usually contains various species of heavy metals, thus understanding of competitive adsorption kinetics of metallic ions in a multi-component system is necessary for developing an innovative adsorption process for wastewater decontamination. In this study, a novel adsorbent, namely nanostructured layered sodium vanadosilicate, was synthesized for concurrent remove of Cu2+, Ni2+ and Co2+ from wastewater in a ternary system, and was characterized by scanning electron microscopy (SEM), Brunauer-Emmet-Teller (BET), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Results showed that the adsorption equilibrium could be reached within 30 min at different metal concentrations and adsorbent dosages, indicating a fast adsorption of Cu2+, Ni2+ and Co2+ by nanostructured layered sodium vanadosilicate, while both pseudo-first- and second-order equations could provide a good description of the observed adsorption kinetics. Moreover, the adsorption capacity and affinity were determined to be in the order of Cu2+ > Co2+ > Ni2+. It was further shown that with increasing the Cu2+ concentration from 5 mg/L to 200 mg/L in the ternary system, the respective adsorption efficiencies of Co2+ and Ni2+ tended to decrease from 97.4% to 26.0%, and 97.3 to 13.3% at an adsorbent dosage of 2.0 g/L. On the other hand, the adsorption efficiency of Cu 2+ was not affected by the increase in the Co2+ and Ni2+ concentrations from 25 to 100 mg/L. Based on the experimental results obtained, the working mechanisms of nanostructured layered sodium vanadosilicates for Ni2+, Co2+ and Cu2+ adsorption could be attributed to ion-exchange with sodium ion, surface electrostatic interaction and the formation of copper vanadium oxide. Consequently, this study clearly showed that nanostructured layered sodium vanadosilicates was an excellent adsorbent for fast and effective removal of soluble Cu2+, Co2+ and Ni2+ in a ternary system, while competitive adsorption among various metal ions revealed in this study may game-change the principles of design and operation of a multi-component system for wastewater treatment.

Automated summary

In this study, a novel nanostructured layered sodium vanadosilicate adsorbent was synthesized for the concurrent removal of Cu2+, Ni2+, and Co2+ from wastewater in a ternary system. The adsorption equilibrium was reached within 30 minutes, indicating fast adsorption kinetics, with Cu2+ showing the highest affinity among the three ions.